Friday 19 March 2010 13.18 EDT
First published on Friday 19 March 2010 13.18 EDT

The government will next week signal a move towards the introduction of a "low-carbon obligation" that would force British Gas and other suppliers of energy to buy a percentage of their power from nuclear and clean coal plants.

The radical measure – an extension of the renewable obligation that is funding wind farms – will appear in a document to be published alongside the budget next Wednesday.

The idea of a low-carbon obligation has been championed by Paul Golby, the chief executive of E.ON UK, which wants to build new nuclear power stations but says they will not run commercially without a change to the market.

The price of carbon was meant to rise through the European commission's emissions trading scheme (ETS), pushing up the price of oil, gas and coal and thus encourage greener technologies.

The Department of Energy and Climate Change has considered imposing a floor on the carbon price – supported by some nuclear generators such as EDF of France – but critics believe it would be legally difficult to implement because it could interfere with the working of the ETS.

Well-placed sources said there would be no hard recommendations contained in the energy market assessment to be published on budget day. It would instead reveal a "narrowing of options" that would give a clear indication about the way ministers were travelling. "There is no hurry from industry to come up with a quick solution to how life will be as far out as 2050, just pressure to do the work thoroughly," said the source.

Government thinking is now clearly different to that of the Conservatives over how to help nuclear without direct public subsidies, which both parties have ruled out. But a low-carbon obligation will still be seen as a backdoor subsidy by those opposed to nuclear, such as Greenpeace.

The Tories said they were prepared to implement a floor on the carbon price and boasted there would be "no limit" on the number of nuclear plants they envisaged being built.

Energy spokesman Greg Clark argued it was vital to provide energy security and combat climate change. "This is a very clear statement that we are in favour of nuclear power," he said, arguing that a Conservative government hoped to preside over the opening of a new atomic power station every 18 months.

But Simon Hughes, energy and climate change spokesman for the Lib Dems, said nuclear power required huge amounts of public money at a time when the taxpayer could least afford it."Blindly pledging to build a new nuclear plant every 18 months is a recipe for disaster," he said

Industry figures were sceptical about whether it would be possible to deliver a massive pipeline of schemes, given planning constraints and shortages of skills and capacity.